1. Field of the Invention
The present invention relates to a cutting apparatus using water containing abrasive grains.
2. Description of the Background Art
A description is given of conventional cutting apparatus and cutting method using water containing abrasive grains. This method was invented for the purpose of improving machining efficiency of a method of cutting a workpiece by jetting high-pressure water to the workpiece (so-called waterjet cutting) (for example, Japanese Patent Laying-Open No. 2000-000767, pages 2–4, FIGS. 1–4). The method uses, as an abrasive (abrasive grains), garnet, silica sand or cast steel grit for example. The abrasive in wet state is supplied from an abrasive tank via an abrasive supply pipe and, from an abrasive supply inlet, into a mixing chamber of an abrasive nozzle head. Here, the wet abrasive is fed (pressure-fed) into the mixing chamber by high-pressure air generated by a compressor. In the mixing chamber, the abrasive is mixed with a high-pressure waterjet and the resultant abrasive waterjet containing the abrasive is emitted from an abrasive nozzle. The abrasive waterjet having been used for cutting is passed through grooves in a table (fixing table) which supports a work (material to be cut) and thereafter collected by a catcher (see Japanese Patent Laying-Open No. 2000-000767, pp. 2–4, particularly FIG. 4 of FIGS. 1–4). The abrasive is collected by a sieve and the collected abrasive still in the wet state is returned as it is to the abrasive tank for reuse (see Japanese Patent Laying-Open No. 2000-000767, pp. 2–4, particularly FIG. 1 of FIGS. 1 to 4).
In recent years, the above-described cutting method using water containing abrasive grains has also been applied to the case where an encapsulated body in which chip-like components (semiconductor chips and the like) mounted on a circuit board are encapsulated all together in resin is cut along cutting lines intersecting at right angles in a grid pattern. In this case, high-precision cutting positions and a cutting width of approximately 200 μm are required.
However, according to the conventional technique, in the case where an encapsulated body as described above is cut, it is necessary to replace, after cutting the encapsulated body along cutting lines in one direction, the original table having grooves with a new table having grooves extending in a direction different from that of the grooves of the original table by 90°. It is further necessary to align the encapsulated body with respect to the new table for setting it again on the table and thereafter cut the encapsulated body along cutting lines in another direction. A reason for performing these operations is that, for the purpose of avoiding wear of the table (fixing table) supporting the work (encapsulated body to be cut), it is necessary to allow an abrasive waterjet to pass through the grooves provided in the table (see Japanese Patent Laying-Open No. 2000-000767, pp. 2–4, Table 14 in FIG. 4 of FIGS. 1–4). Accordingly, the abrasive waterjet having been used for cutting the work (encapsulated body) supported on the new table is passed through the grooves and thereafter collected by the catcher without contacting the new table. This technique requires two tables and thus the cost for the apparatus is increased. Further, since it is necessary to align the encapsulated body with respect to the new table for setting it again on the new table, working efficiency is reduced. Furthermore, the dimensional accuracy (such as position and angle) in cutting could be deteriorated.